An embodiment of the present invention relates generally to integrated hydrostatic transaxles, and more particularly, to an external cooling circuit and adapter for use with integrated hydrostatic transaxles.
Hydrostatic traction drive technology is commonly employed in the turf care industry. Recently, the trend has been toward the use of integrated hydrostatic transaxles in lawn care machines for the consumer and professional lawn mower markets, particularly in “zero-turn”-type machines. The integrated transaxles combine all of the hydrostatic drive functions (e.g., hydraulic pump, motor, and the like) into a single housing, which makes it very economical for machine manufacturers to utilize hydrostatic traction drives. Cooling an integrated transaxle is typically performed by a fan mounted on, and driven by, the transaxle input shaft. The only required external connection is a single hose coupled to an overflow bottle, which is very similar to the overflow bottle commonly used on automotive engine cooling systems.
However, in certain applications it has been difficult or impossible to get enough cooling to the transaxle to allow operation at the desired speeds and loads. Common approaches to addressing overheating include (i) using various means to direct air as close to ambient temperature as possible to the cooling fans; (ii) directing air from the fans over the transaxles to provide the most cooling possible; (iii) reducing loads on the transaxle to reduce heat; and (iv) reverting to non-integrated hydrostatic solutions.
While solutions (i) and (ii) are fairly simple to implement, these methods do not always provide sufficient cooling capacity. For solution (iii), a reduction of load means slowing the machine or reducing the rate at which the machine performs work. This is undesirable, particularly if the machine is in commercial use. In particular, the owner of a commercial machine typically earns payment for work performed and the faster the machine can operate, the more income and profits can be generated. Finally, solution (iv) results in higher production costs due to the need for each individual component to have its own housing, fittings, tubes, hoses, and the like, as well as the cost of labor for assembling these components.
Some hydrostatic transaxle models, particularly those intended for commercial applications, include charge pumps and oil filters as part of the transaxle assembly. These systems use the transaxle casing as a reservoir and an overflow bottle to maintain oil levels. It is desirable to leverage this structure in order to provide additional cooling to the integrated transaxle.
Further, assembly lines for integrated hydrostatic transmissions are not set up for remote, external circulation of transaxle oil during the test procedures. In normal integrated testing, the filter is installed on the transaxle, the case is filled with oil, testing is completed, and the fill port sealed for shipment to the OEM customer. There are no known approaches for external circulation since this is an entirely new concept. However, several principles must be considered. First, providing an additional test station on the assembly line, particularly to an existing line, is expensive and burdensome. Second, solutions requiring opening of the system after testing are messy (due to potential oil loss) and still require substantial variation of the assembly process. Third, transferring the burden to the customer is not ideal.
It is therefore desirable to provide an integrated transaxle capable of external circulation without significantly modifying the assembly line and without creating a mess.